STL-queue.back()队尾误区
queue.back()指向最新插入queue中的值,而非隊尾元素,
如:queue.pop()多次,并不會影響queue.back()的值。
STL 英文back()解釋:
reference& back();
const_reference& back() const;
Access last element
Returns a reference to the last element in the?queue. This is the "newest" element in the queue (i.e. the last element pushed into the?queue).
This member function effectively calls member?back?of the underlying container object.
queue.front()指向最舊插入queue的元素值。
STL 英文front()解釋:
reference& front(); const_reference& front() const;Access next element
Returns a reference to the?next element?in the?queue.
The?next element?is the "oldest" element in the?queue?and the same element that is popped out from the?queue?when?queue::pop?is called.
This member function effectively calls member?front?of the?underlying container?object.
判斷隊列為空使用empty或者front,不能使用back查看。
// queue::front #include <iostream> // std::cout #include <queue> // std::queueint main () {std::queue<int> myqueue;myqueue.push(77);myqueue.push(16);std::cout<<myqueue.back()<<std::endl;std::cout<<myqueue.front()<<std::endl;myqueue.pop();std::cout<<myqueue.back()<<std::endl;std::cout<<myqueue.front()<<std::endl;myqueue.pop();std::cout<<myqueue.back()<<std::endl;std::cout<<myqueue.front()<<std::endl;std::cout << "myqueue.front() is now " << myqueue.front() << '\n';return 0; }queue::front - C++ Reference
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